import sun.reflect.generics.tree.Tree;

import javax.transaction.TransactionRequiredException;
import java.util.LinkedList;
import java.util.Queue;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * user:likai
 * Date:2022-11-22
 * Time:16:55
 */
public class BinaryTree {
     class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode node1=new TreeNode('a');
        TreeNode node2=new TreeNode('b');
        TreeNode node3=new TreeNode('c');
        node1.left=node2;
        node1.right=node3;
        TreeNode node4=new TreeNode('d');
        node3.right=node4;
        return node1;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root==null){
            return;
        }
        System.out.print(root.val);
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root==null){
            return;
        }
        inOrder(root.left);
        System.out.print(root.val);
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root==null){
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val);
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    int size(TreeNode root) {
        Queue<TreeNode> queue=new LinkedList<>();
        if(root==null){
            return nodeSize;
        }
        queue.add(root);
        while(!queue.isEmpty()){
            TreeNode node=queue.poll();
            nodeSize++;
            if(node.right!=null){
                queue.offer(node.right);
            }
            if(node.left!=null){
                queue.offer(node.left);
            }

        }
        return nodeSize;
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if(root==null){
            return 0;
        }
        return size2(root.left)+size2(root.right)+1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root==null){
            return;
        }
        Queue<TreeNode> queue=new LinkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode node=queue.poll();
            if(node.right==null&&node.left==null){
                leafSize++;
            }else{
                if(node.right!=null){
                    queue.offer(node.right);
                }
                if(node.left!=null){
                    queue.offer(node.left);
                }
            }
        }

    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if(root==null){
            return 0;
        }
        if(root.left==null&root.right==null){
            return 1;
        }
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        Queue<TreeNode> queue=new LinkedList<>();
        if(root==null){
            return 0;
        }
        queue.offer(root);
        int n=1;
        while(!queue.isEmpty()&&n<k){
            int length=queue.size();
            for (int i = 0; i < length; i++) {
                TreeNode cur=queue.poll();
                if(cur.left!=null){
                    queue.offer(cur.left);
                }
                if(cur.right!=null){
                    queue.offer(cur.right);
                }
            }
            n++;
        }
        if(queue.isEmpty()){
            return -1;
        }
        return queue.size();
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if(root==null){
            return 0;
        }
        int left=getHeight(root.left);
        int right=getHeight(root.right);
        return left>right?left+1:right+1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root==null){
            return null;
        }
        if(root.val==val){
            return root;
        }
        TreeNode left=find(root.left,val);
        if(left!=null){
            return left;
        }
        TreeNode right=find(root.right,val);
        if(right!=null){
            return right;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        Queue<TreeNode> queue=new LinkedList<>();
        if(root==null){
            return ;
        }
        queue.offer(root);
        while(!queue.isEmpty()){
            int length=queue.size();
            for (int i = 0; i < length; i++) {
                TreeNode cur=queue.poll();
                System.out.print(cur.val+" ");
                if(cur.left!=null){
                    queue.offer(cur.left);
                }
                if(cur.right!=null){
                    queue.offer(cur.right);
                }
            }
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        Queue<TreeNode> queue=new LinkedList<>();
        if(root==null){
            return true;
        }
        if(root.left==null&&root.right==null){
            return false;
        }
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode node=queue.poll();
            if(node.left==null&&node.right!=null){
                return false;
            }
            if(node.left==null){
                break;
            }
            queue.offer(node.left);
            queue.offer(node.right);
        }
        while(!queue.isEmpty()){
            TreeNode cur=queue.poll();
            if(cur.left!=null||cur.right!=null){
                return false;
            }
        }
        return true;
    }
}
